Application of a mass consistent flow model to study the CO2 mass balance of forests

Abstract

The reconstruction of the wind field is one of the main issues in the mass conservation approach for calculation of CO 2 advection in forest ecosystems and still remains a challenging problem. In the current study, we present an advancement of this approach: the use of a mass consistent flow model (WINDS) which takes into account measured wind data and simulates the 3-D flow field, while imposing air mass conservation in the control volume. We apply the WINDS model to calculate half hourly mean total advective flux terms at the arboEurope-IP site of Renon (Bozen/Bolzano Autonomous Province), in Northern Italy. The data used refer to six time periods of one day representing three different meteorological conditions observed during the ADVEX campaign from April to September 2005. Current results are compared with results obtained in two other studies for the same time periods. One of these studies is based on the mass conservation approach as well, but applies only interpolations to reconstruct the wind field; the other study makes use of tilt correction (sectorwise planar fit method) for the vertical wind component. In the present study, the effect of the wind field reconstruction method on the estimation of the advective fluxes is discussed. The possibility of using reduced input wind data (i.e. number of towers) for WINDS is also investigated. The results suggest that the representativeness of wind tower measurements is of primary importance for estimating CO 2 advection terms and their uncertainty in complex terrain.

Direct advection measurements do not help to solve the night-time CO2 closure problem: Evidence from three different forests

“…However, if the procedure choice could induce some errors, it is unlikely to create systematic differences between different wind sectors. It is worth noting that the results obtained by Canepa et al (2010), using a mass consistent approach at RE did not contradict our conclusions.…”

Aspects of CO2 advection measurements

“…This was proposed by Aubinet et al (2005) and applied by Vickers and Mahrt (2006), Heinesch et al (2007), Montagnani et al (2010). Canepa et al (2010) used the mass balance approach in combination with modeling. Mahrt (2010) further proposed multitower measurements of w, possibly in combination with aircraft observations.…”

Spatiotemporal evolution of CO2 concentration, temperature, and wind field during stable nights at the Norunda forest site

“…Such conditions were observed, e.g. during the ADVEX campaign in Renon during synoptically dominated strong wind conditions Aubinet et al, 2010;Canepa et al, 2010). However, in Norunda, the situation is different: Horizontal [CO 2 ] differences are much larger than the specification of the Li-6262, which is around AE1 mmol mol À1 .…”